Hello Guys,
I have recently join a new company and development team is used to work in the India working hours and rest of the time the Servers on the AWS are remaining ideal/utilized rest of the day. so they want to reduce the cost so they come to me and ask for the strategy to reduce cost so I suggested to go have shut down the machine/servers in non-working hours which they agree but they want a governing mechanism to enforce this so I have come up with a lambda function which allow them to customized startup and stop time as well as they don't need to manually start and stop the same. As i need to implement the same functionality on the 25 account so I have written a lambda function and then put it in a cloud formation and provided them and ask them to execute this in the account and then just add tag name "schedule" and value of start and stop time in UTC as the lambda is run on the UTC lambda function will take care of the rest.
To further reduce costs of our EC2 instances, we determined some instances that are running 24/7 unnecessarily. An automated process to schedule stop and start instances would greatly help cutting costs. Of course, the solution itself should not add an extra instance to our infrastructure. The solution must be an example of serverless computing.
Automatically stop running EC2 instances 24/7 unnecessarily
We created a lambda function that scans all instances for a specific tag. The tag we use is named ‘Schedule’ and contains the desired ‘runtime’ for the specific instance. Instances without a Schedule tag will not be affected. We support the following content format in the Schedule tag:
08:00-19:15 start the instance at 08:00, stop it at 19:15
21:00-07:45 start the instance at 21:00, stop it at 07:45 the next day
-17:45 stop this instance at 17:45 today
-16:30T Terminate instance at 16:30 today
# whatever Anything starting with a # is totally ignored
21:00-07:45 start the instance at 21:00, stop it at 07:45 the next day
-17:45 stop this instance at 17:45 today
-16:30T Terminate instance at 16:30 today
# whatever Anything starting with a # is totally ignored
NOTE: All times are UTC times!
Invalid tag-content is automatically prefixed with an # so that it is ignored in future invocations of the lambda function. Also instances with only an end-time will have their tag rewritten to avoid restarts at 00:00.
Our lambda function is written in python using boto3 for AWS integration. The function requires a role to be able to interact with EC2. The lambda function has to be able to read and change tags, stop and start instances and even terminate them!
To further automate the process, we need to automatically execute the lambda function, which can be achieved by creating a CloudWatch Event Rule. It is a bit of a funny place for a schedule, but that’s where you configure it. The event will be used as a trigger to start our lambda function.
The scheduler we create in the stack runs the lambda function every 10 minutes, giving your EC2 scheduler a granularity of 6 runs per hour.
As shown in the below screenshot One need to just add the tag “Schedule” and required timing against it and it will start and stop the instance at the given time.
Below is the attached cloud formation template .
{
"AWSTemplateFormatVersion": "2010-09-09",
"Description" : "[INFRA] Lambda code to start/stop EC2 instances based on tag Schedule. Examples of valid content for Schedule tag are: 08:00-18:00 EC2 instance will run from 08:00 till 18:00 every day. -17:00 wil stop the instance today at 17:00 and rewrite the tag to #-17:00. -17:00T will TERMINATE the instance at 17:00. Any invalid content will be rewritten to start with a #. Any content starting with # will be ignored",
"Resources" : {
"EC2SchedulerLambda": {
"Type": "AWS::Lambda::Function",
"Properties": {
"Handler": "index.EC2Scheduler",
"FunctionName" : "EC2Scheduler",
"Description" : "[INFRA] Lambda code to start/stop EC2 instances based on tag Schedule. NOTE times are UTC. See stack description for further information",
"Role": { "Fn::GetAtt" : ["EC2SchedulerRole", "Arn"] },
"Code": {
"ZipFile": { "Fn::Join": ["\n", [
"from datetime import datetime, time",
"import boto3",
"import re",
"",
" theTag='Schedule'",
"",
"doLog = True",
"",
"def EC2Scheduler(event, context):",
"",
" now = datetime.now().replace(second=0, microsecond=0)",
"",
" if doLog:",
" print 'Reference time is ', now.time()",
"",
" ec2 = boto3.resource('ec2')",
"",
" allInstances = ec2.instances.filter(Filters=[{'Name': 'instance-state-name', 'Values': ['running', 'stopped']}])",
"",
" for instance in allInstances:",
" if instance.tags :",
" for tag in instance.tags:",
" if tag['Key'] == theTag :",
" Range=tag['Value']",
"",
" if doLog :",
" print instance.instance_id, ",
"",
" shouldrun=shouldRunNow(instance, now, Range)",
"",
" if doLog :",
" print 'should %s' %( 'run' if shouldrun else 'NOT run'),",
"",
" alignInstance(instance, shouldrun)",
"",
"def shouldRunNow(instance, now, tRange):",
"",
" currentState = instance.state['Code'] == 16",
"",
" # is the tRange commented out",
"",
" if tRange[0:1] == '#':",
" if doLog:",
" print 'Range starts with # -- no changes',",
" return currentState",
"",
" # does the time indicate an end-time only [eg -13:15]",
"",
" if tRange[0:1] == '-':",
" tEnd=time(int(tRange[1:3]),int(tRange[4:6]))",
"",
" if doLog:",
" print 'End time:', tEnd,",
"",
" if now.time() > tEnd:",
"",
" msg='stop'",
" if tRange[6:7] == 'T':",
"",
" terminateAllowed=instance.describe_attribute(Attribute='disableApiTermination')['DisableApiTermination']['Value'] == False",
"",
" if terminateAllowed:",
" instance.modify_attribute( Attribute='instanceInitiatedShutdownBehavior', Value='terminate' )",
" msg='terminate'",
" else:",
" msg='stop [terminate not allowed]'",
"",
" # re-tag",
"",
" instance.delete_tags(Tags=[{'Key': theTag, 'Value': tRange}])",
" instance.create_tags(Tags=[{'Key': theTag, 'Value': '#'+msg+'@'+tRange}])",
"",
" if doLog:",
" print 'time to ', msg, ",
"",
" return False",
"",
" else:",
" # leave instance in current state",
" if doLog:",
" print 'NO time to stop (yet) ',",
" return currentState",
"",
" # some simple checks for tRange",
"",
" if not re.match('\\d{2}:\\d{2}-\\d{2}:\\d{2}',tRange):",
" if doLog:",
" print 'error in format of tag: >', tRange, '< -- no changes required ',",
"",
" instance.delete_tags(Tags=[{'Key': theTag}, {'Value': tRange}])",
" instance.create_tags(Tags=[{'Key': theTag, 'Value': '# Err: '+tRange}])",
"",
" return currentState",
"",
" tStart=time(int(tRange[0:2]),int(tRange[3:5]))",
" tEnd=time(int(tRange[6:8]),int(tRange[9:11]))",
"",
" inInterval = False",
" ",
" # first case, start < end --> same day",
"",
" if tStart < tEnd:",
" if tStart <= now.time() <= tEnd: ",
" inInterval = True ",
"",
" # second case, end < start --> carry over to next day",
"",
" else:",
" if tStart <= now.time() <= time(23,59) or time(0,0) <= now.time() <= tEnd:",
" inInterval = True",
"",
" if doLog :",
" print 'Ref time is %s interval' %( 'in' if inInterval else 'NOT in'), tRange, ",
"",
" return inInterval",
"",
"def alignInstance(inst, requiredOn):",
"",
" actualOn = inst.state['Code'] == 16 ",
" msg='is compliant'",
"",
" if actualOn != requiredOn:",
" if requiredOn == True:",
" msg='starting'",
" inst.start()",
" else:",
" termReq=inst.describe_attribute(Attribute='instanceInitiatedShutdownBehavior')['InstanceInitiatedShutdownBehavior']['Value'] == 'terminate'",
"",
" if termReq:",
" msg='terminating'",
" inst.terminate()",
" else:",
" msg='stopping'",
" inst.stop()",
"",
" if doLog:",
" print '-->', msg",
""
]]}
},
"Runtime": "python2.7"
}
},
"EC2SchedulerTick": {
"Type": "AWS::Events::Rule",
"Properties": {
"Description": "ScheduledRule for EC2Scheduler",
"ScheduleExpression": "rate(10 minutes)",
"Name" : "EC2SchedulerTick",
"State": "ENABLED",
"Targets": [{
"Arn": { "Fn::GetAtt": ["EC2SchedulerLambda", "Arn"] },
"Id": "TargetFunctionV1"
}]
}
},
"PermissionForEventsToInvokeLambda": {
"Type": "AWS::Lambda::Permission",
"Properties": {
"FunctionName": { "Ref": "EC2SchedulerLambda" },
"Action": "lambda:InvokeFunction",
"Principal": "events.amazonaws.com",
"SourceArn": { "Fn::GetAtt": ["EC2SchedulerTick", "Arn"] }
}
},
"EC2SchedulerRole": {
"Type": "AWS::IAM::Role",
"Properties": {
"AssumeRolePolicyDocument": {
"Version": "2012-10-17",
"Statement": [{ "Effect": "Allow", "Principal": {"Service": ["lambda.amazonaws.com"]}, "Action": ["sts:AssumeRole"] }]
},
"Path": "/",
"RoleName" : "EC2SchedulerRole",
"Policies": [{
"PolicyName": "EC2SchedulerPolicy",
"PolicyDocument": {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": ["logs:*"],
"Resource": "arn:aws:logs:*:*:*"
},
{
"Effect": "Allow",
"Action": ["ec2:*"],
"Resource": "*"
}]
}
}]
}
}
}
}
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